Stator assembly with an overmolding that secures magnets to a flux ring and the flux ring to a stator housing

ABSTRACT

A stator assembly for an electric motor includes a stator housing, an expandable flux ring inserted into the stator housing and a plurality of magnets on an inner surface of the flux ring. Overmold material is molded around the magnets in the flux ring, such as by injection molding. The pressure of the overmold material as it is being molded expands the flux ring pressing the flux ring into engagement with the stator housing. The overmold material secures the magnets to the flux ring and the flux ring to the housing. One of the flux ring and stator housing has a dimple that engages a hole in the other of the flux ring and stator housing to align the flux ring and stator housing. In an aspect, the overmold material is molded to form at least one of a commutator end or rear bearing support, front bearing support and fan baffle. In an aspect, the overmold material is molded to form a keying feature. The keying feature can be slots of different widths between magnetic poles of the stator assembly. In an aspect, the flux ring and housing are preformed as a unit by stamping them from blanks and rolling them together. In a variation, the flux ring blank is rolled first to form the flux ring and the housing blank rolled around the flux ring with the flux ring acting as a rolling arbor.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/468,643 filed Aug. 20, 2003, which is a § 371National Phase filing of PCT International Application PCT/US02/05029filed Feb. 22, 2002 (International Publication Number WO 02/068235 A2)which claims the benefit of U.S. Provisional Application No. 60/271,141filed Feb. 23, 2001. This application claims the benefit of U.S.Provisional Application No. 60/433,496 filed Dec. 13, 2002. Thedisclosures of the above applications are incorporated herein byreference.

FIELD OF THE INVENTION

[0002] The present invention relates to electric motors, and moreparticularly to stator assemblies for electric motors.

BACKGROUND OF THE INVENTION

[0003] In the construction of stator assemblies for permanent magnetelectric motors, magnets are retained within the stator assembly. Forexample, in a brush-type permanent magnet electric motor, magnets areretained on a stator housing or a separate flux ring within the statorhousing. This generally requires gluing or adhering each individualmagnet to the flux ring or stator housing.

[0004] Various types of adhesives have been used to adhere the magnetsto the metallic surface. It is possible that a sudden shock to theelectric motor will destroy the bond between the magnet and the fluxring or stator housing. This would result in movement of the magnetwithin the stator assembly. The magnet itself could even break. As aresult, the electric motor ceases to properly function.

[0005] It is known in the art to provide an anchor in the flux ring orstator housing. Magnetic material is then injection molded on the fluxring or stator housing and is retained in position by the anchor. Suchan anchor system is disclosed in U.S. Pat. No. 6,522,042 issued Feb. 18,2003 entitled Anchoring System for Injection Molded Magnets on a FluxRing or Motor Housing and in U.S. application Ser. No. 09/764,004 filedJan. 17, 2001 entitled Anchoring System for Injection Molded Magnets ona Flux Ring or Motor Housing. However, a disadvantage of the anchoringsystems described in the above-identified patent applications is thatthey require the use of injection molded magnetic material. This istypically the most expensive type of magnetic material per unit flux.

SUMMARY OF THE INVENTION

[0006] Accordingly, the present invention provides a stator assembly foran electric motor. The stator assembly includes a stator housing, asplit flux ring inserted into the stator housing and a plurality ofmagnets on an inner surface of the flux ring. An overmolding secures themagnets to the flux ring and asserts a radial force on the flux ring tosecure it to the stator housing. Additionally, the overmolding fills theseam of the flux ring and prevents collapse of the flux ring.

[0007] In an aspect of the invention, the material used to mold theovermolding is a plastic that is injection molded about the magnets onthe flux ring after the flux ring and magnets have been placed in thestator housing. The pressure of the plastic as it is being injectionmolded exerts a radial pressure on the flux ring, expanding it againstthe stator housing and secures it to the stator housing. The overmoldingalso secures the magnets to the flux ring.

[0008] In an aspect of the invention, the flux ring is aligned with thestator housing and is further secured to it by engagement of a dimple inone of the flux ring and stator housing with a hole in the other of theflux ring and the stator housing.

[0009] In an aspect of the invention, at least one of a rear bearingsupport, front bearing support and fan baffle are integrally molded withthe overmolding when the material used to mold the overmolding ismolded.

[0010] In an aspect of the invention, the overmolding is formed withslots of different widths between magnetic poles of the stator assemblyto provide a keying feature for the stator assembly to key it, such aswhen it is placed in a magnetizer.

[0011] In an aspect of the invention, the flux ring and housing arepreformed as a unit by stamping them from blanks and rolling themtogether. In a variation, the flux ring blank is rolled first to formthe flux ring and the housing blank rolled around the flux ring with theflux ring acting as a rolling arbor.

[0012] In an aspect of the invention, an electric motor has an armatureand a stator assembly in accordance with the invention.

[0013] In an aspect of the invention, a power tool has a housingincluding an electric motor having an output coupled to a transmission.The electric motor has an armature and a stator assembly in accordancewith the invention.

[0014] Further areas of applicability of the present invention willbecome apparent from the detailed description provided hereinafter. Itshould be understood that the detailed description and specificexamples, while indicating the preferred embodiment of the invention,are intended for purposes of illustration only and are not intended tolimit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

[0016]FIG. 1 is a cross-sectional view of a power tool according to thepresent invention;

[0017]FIG. 2 is a perspective view of a stator assembly of the powertool of FIG. 1;

[0018]FIG. 3 is a cross-section view of the stator assembly of FIG. 2taken along the line 3-3;

[0019]FIG. 4 is a perspective view of a flux ring of the stator assemblyof FIG. 2;

[0020]FIG. 5 is a perspective view of a stator can or housing of thestator assembly of FIG. 2;

[0021]FIG. 6 is a perspective view of the flux ring of FIG. 4 receivedin the stator can of FIG. 5;

[0022]FIG. 7 is a perspective view of a variation of the flux ring ofFIG. 4 showing a flux ring with interlocking fingers;

[0023]FIG. 8 is a cross-sectional view of an alternative configurationof the stator assembly of FIG. 2;

[0024]FIG. 9 is a perspective view of an electric motor having analternative configuration of the stator assembly of FIG. 2;

[0025]FIG. 10 is a cross-sectional view of the electric motor of FIG. 9taken along the line 10-10;

[0026]FIG. 11 is a perspective view of an alternative stator assembly;and

[0027]FIG. 12 is a perspective view of still another alternative statorassembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The following description of the preferred embodiments is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

[0029] Referring now to FIG. 1, a power tool 10 is shown. The power tool10 is illustrated as a drill, however, any type of power tool may beused in accordance with the present invention. The power tool 10includes a housing 12 which surrounds a motor 14. An activation member16 is coupled with the motor and a power source 18. The power source 18includes either a power cord (AC current) or includes a battery (DCcurrent) (not shown). The motor 14 is coupled with an output 20 thatincludes a transmission 22 and a chuck 24. The chuck 24 is operable toretain a tool (not shown).

[0030] The motor includes a stator assembly 30. The stator assembly 30includes a stator housing 32, a flux ring 34 and magnets 36. The fluxring 34 is an expandable or split flux ring. An armature 40 includes ashaft 42, a rotor 44 and a commutator 50 coupled with the shaft 42. Therotor 44 includes laminations 46 and windings 48. The motor 14 alsoincludes end plates 52 and 54. End plate 52 includes a front bearing 56which supports one end of a shaft 42. The shaft 42 is coupled with apinion 60 that is part of the output 20. Brushes 62 and 64 areassociated with the commutator 50. A rear bearing 70 is also coupledwith the end plate 54 to balance rotation of the shaft 42.

[0031] Referring now to FIGS. 2-6, the stator assembly 30 is describedin further detail. Stator housing 32 and flux ring 34 are illustrativelymade of soft magnetic material, such as cold rolled steel. The flux ring34 has anchors 80 extending radially inward. The magnets 36 are disposedaround an inner surface 82 of the flux ring 34 between anchors 80. Anovermolding 84 secures the magnets 36 to flux ring 34 as described inmore detail in WO 02/068235 A2.

[0032] The flux ring 34 is discontinuous having a seam 86 extendingtherealong. The seam 86 enables the flux ring 34 to be compressed forinsertion into the stator housing 32. When flux ring 34 is assembled instator assembly 30, the seam 86 is preferably disposed over one ofmagnetic poles P₁, P₂ of the stator assembly 30 to minimize magneticlosses. In the configuration of FIGS. 2-6, the flux ring 34 includes aprojection or dimple 88 that engages a hole 90 in the stator housing 32.Alternatively, as shown in FIG. 8, the stator housing 32 includes aprojection or dimple 92 that engages a hole 94 in the flux ring 34.Engagement of the dimple 88,92 and hole 90,94 provides proper alignmentof the flux ring 34 during assembly of the stator assembly 30. Thedimple 88,92 and hole 90,94 are illustratively at ninety degrees to seam86 to provide sufficient displacement of dimple 88 or hole 94, asapplicable, in flux ring 34 with respect to stator housing 32 when fluxring 34 is compressed so that when flux ring 34 is uncompressed, dimple88 will be urged into hole 90 (or hole 94 around dimple 92).Alternatively, the dimple 88, 92 and hole 90, 94 are ideally centeredover one of the magnetic poles P₁, P₂ to reduce magnetic losses.Overmolding 84 is formed so there are slots 95, 96 on diametricallyopposite sides of flux ring 34 between the overmolding 84 around magnets36 of pole P₁, and the overmolding 84 around magnets 36 of pole P₂.Slots 95, 96 illustratively extend axially along inner surface 82 offlux ring 34 between poles P₁ and P₂. Slots 95, 96 may be gaps in theovermolding 84 or regions of reduced thickness in the overmolding 84. Inthe illustrative embodiment, stator assembly 30 has one pair of magneticpoles, with one of poles P₁ and P₂ thus being a North pole and the otherbeing a South pole. It should be understood that stator assembly 30could have more than one pair of North and South poles.

[0033] To assemble the stator assembly 30, stator housing 32 and fluxring 34 are each preformed. In this regard, stator housing 32illustratively has interlocking fingers 33 as shown in FIG. 5. The fluxring 34 is slightly compressed and inserted into the stator housing 32as shown in FIG. 6. The dimple 88,92 engages the hole 90,94 as describedabove. The magnets 36 are placed against the inner surface 82 of theflux ring 34 and are positioned between the anchors 80. The magnets 36can be lightly magnetized so they are retained against the inner surface82 of flux ring 34 during assembly.

[0034] Overmold material 83, such as plastic, is injection molded intothe stator assembly 30 to form the overmolding 84. During the injectionmolding process, the pressure of the overmold material 83 pushes againstthe magnets 36 and flux ring 34, expanding the flux ring 34 against thestator housing 32. The overmold material 83 fills the seam 86 of fluxring 34 and surrounds the magnets 36. Expansion of the flux ring 34against the stator housing 32 provides the retention force for retainingthe flux ring 34 within the stator housing 32. Further, because theovermolding 84 fills the seam 86 of the flux ring 34, compression of theflux ring 34 in the stator housing 32 is prevented after the overmoldmaterial 83 hardens, thus preventing the removal of flux ring 34 fromthe stator housing 32. The engagement of the dimple 88, 92 and hole 90,94, held in place by the overmolding 84, further secures the flux ring34 to the stator housing 32. The diameter and true position of theovermolding 84 are maintained closely relative to the inside diameter ofthe stator housing 32 to reduce tolerance stack-ups to the armature 40(FIG. 1). It should be understood that there can be more than onedimple/hole arrangement in flux ring 34 and stator housing 32.

[0035] In an aspect of the invention, slot 95 is wider than slot 96.This limits to two the orientations in which stator assembly 30 can beplaced in a magnetizer (not shown) used to magnetize magnets 36 afterstator assembly 30 is assembled. That is, the difference in the widthsof slots 95 and 96 provide a keying feature that keys stator assembly 30to the magnetizer. If the widths of slot 95 and 96 were the same, statorassembly 30 could be placed in the magnetizer in four orientations. Thatis, either end of stator assembly 30 could be placed in the magnetizerin two orientations that are 180 degrees apart. By forming the keyingfeature in the overmolding 84, each end of the stator assembly 30 can beplaced in the magnetizer in only one orientation, reducing to two theorientations in which the stator assembly 30 can be placed in themagnetizer. This makes sensing of the stator assembly 30 in themagnetizer fixture more robust and eliminates the possibility ofmagnetizing backwards due to placing the stator assembly 30 in themagnetizer in the wrong orientation. It should be understood that instator assemblies having more than two poles, preferably the width ofonly one of the slots between the poles would be different than thewidths of the rest of the slots between the poles to key the statorassembly to the magnetizer.

[0036] In an aspect of the invention, the stator housing 32 and the fluxring 34 are preassembled as a unit according to an alternative assemblymethod. More specifically, the stator housing 32 and flux ring 34 areformed of separate blanks, such as steel blanks, and in this regard, theedges of the seams of flux ring 34 and stator housing 32 are formed tohave interlocking fingers, such as interlocking fingers 33 shown in FIG.5 for stator housing 32 and interlocking fingers 37 shown in FIG. 7 forflux ring 34. One or more holes 94 are stamped into the flux ring andmatching mating dimple(s) 92 stamped in the stator housing 32, orvice-versa. The stator housing 32 and flux ring 34 are lain together intheir flat, pre-rolled states with the holes and dimples engaged. Thestator housing 32 and flux ring 34 are rolled and the seam of the fluxring 34 interlocks as does the seam of the stator housing 32. The holesand dimples maintain alignment of the stator housing 32 and flux ring 34during the rolling process.

[0037] In an alternative, the flux ring 34 can be rolled first and thestator housing 32 rolled about the flux ring 34. In this case, the fluxring 34 acts as a rolling arbor. Additionally, the holes and dimplesmaintain alignment as the stator housing 32 is rolled about the fluxring 34. According to another alternative, the stator housing 32 andflux ring 34 can be spot-welded together to form a sub-assembly.Regardless of how the stator housing 32 and flux ring 34 are assembledtogether, injection of the overmold material 83 not only secures themagnets 36 to the flux ring 34 but also secures the flux ring 34 to thestator housing 32 through the pressure exerted on the flux ring 34therein.

[0038] The stator assembly 30 of the present invention providessignificant advantages in both assembly and manufacture of the powertool 10. In particular, the stator assembly 30 eliminates the need forwelding equipment to secure the components together. The expansion offlux ring 34 against stator housing 32 induced by injection of theovermold material 83 secures the flux ring 34 to stator housing 32 andthe overmolding 84 also secures the magnets to flux ring 34. Theinterlocking of the dimple/hole arrangement(s) further secure the fluxring 34 to the stator housing 32. Further, injection of the overmoldmaterial 83 reduces tolerance stack-ups, improving ease of assembly. Asa result, manufacturing equipment and floor space is reduced entailingcost savings. Another advantage of reduced tolerance stack-ups is thatthe magnet can be placed closer to the armature 40 thus maximizing motorperformance. The keying feature provided by the different widths ofslots 95, 96 improve the placement of stator assembly 30 in themagnetizer.

[0039] Turning now to FIGS. 9 and 10, an electric motor 98 having afurther embodiment of the stator assembly 30, indicated generally byreference numeral 100, is shown. The stator assembly 100 includes thestator housing 32, flux ring 34, and permanent magnets 36 as shown inthe stator assembly 30 of FIGS. 2-6. The stator assembly 100 furtherincludes an integrally molded commutator end or rear bearing support 102and an integrally molded fan baffle 104. An armature, such as armature40 (FIG. 1), is received in stator assembly 100. A fan 112 is affixed atone end of shaft 42 of armature 40 and is disposed within fan baffle104. An insulative sleeve 114 may illustratively be disposed betweenshaft 42 and laminations 46 and between shaft 42 and commutator 50. Anend plate (not shown in FIGS. 9 and 10), such as end plate 52 (FIG. 1),is affixed to fan baffle 104.

[0040] The rear bearing support 102 includes a cap 106 integrally moldedfrom the overmold material 83. The cap 106 includes a pocket 108 forreceiving rear bearing 70 (FIG. 1). Integrally forming the cap 106 aspart of the overmolding 84 from the overmold material 83 eliminates theneed for separate fasteners to fix the rear bearing support 102 to thestator housing 32. The fan baffle 104 is likewise integrally molded fromthe overmold material 83.

[0041] Turning now to FIG. 11, an alternate embodiment of statorassembly 100 is shown and generally indicated by reference numeral 100′.Stator assembly 100′ is substantially similar to the stator assembly 100shown in FIGS. 9 and 10, however, only the rear bearing support 102 isintegrally molded as part of the overmolding 84 from the overmoldmaterial 83. Alternatively, a front bearing support 103 (shown inphantom in FIG. 11) for engaging a front bearing, such as bearing 56(FIG. 1), may be integrally molded in a manner substantially similar tothe rear bearing support 102.

[0042] With reference to FIG. 12, another alternate embodiment of statorassembly 100 is illustrated and generally indicated by reference numeral100″. Stator assembly 100″ is substantially similar to the statorassembly 100 shown in FIGS. 9 and 10, however, only the fan baffle 104is integrally molded as part of overmolding 84 from the overmoldmaterial 83.

[0043] By integrally molding the commutator end bearing support 102 andthe fan baffle 104 as part of overmolding 84, further assembly and costssavings may be realized.

[0044] The description of the invention is merely exemplary in natureand, thus, variations that do not depart from the gist of the inventionare intended to be within the scope of the invention. Such variationsare not to be regarded as a departure from the spirit and scope of theinvention.

What is claimed is:
 1. A stator assembly, comprising: a housing; a fluxring disposed within the housing; a plurality of permanent magnetsdisposed around an inner surface of the flux ring; and a materialovermolded around the plurality of magnets to secure the magnets to theflux ring and to secure the flux ring to the housing.
 2. The statorassembly of claim 1, wherein the flux ring includes anchors extendingradially inward with the plurality of permanent magnets disposed betweenthe anchors.
 3. The stator assembly of claim 1, wherein the flux ringincludes a seam that allows the flux ring to be compressed for insertioninto the housing during assembly, the overmold material expanding theflux ring against the housing.
 4. The stator assembly of claim 3 whereinthe seam of the flux ring is filled with the overmold material duringmolding of the overmold material, the overmold material upon hardeningpreventing the flux ring from compressing.
 5. The stator assembly ofclaim 3 wherein the stator assembly has a plurality of magnetic poles,the seam of the flux ring aligned with one of the magnetic poles.
 6. Thestator assembly of claim 3, wherein one of the flux ring and the housingincludes at least one projection and the other of the flux ring and thehousing includes at least one hole, the projection being received in thehole to align the flux ring in the housing.
 7. The stator assembly ofclaim 6, wherein the projection and hole of the flux ring and housingare disposed about ninety degrees from the seam of the flux ring.
 8. Thestator assembly of claim 1, further including at least one of a rearbearing support, front bearing support and fan baffle integrally formedof the overmold material during molding of the overmold material.
 9. Thestator assembly of claim 1, further including a rear bearing supportintegrally formed of the overmold material during molding of theovermold material, the rear bearing support including a cap having apocket therein for receiving a rear bearing.
 10. The stator assembly ofclaim 1, wherein the overmold material is a plastic.
 11. The statorassembly of claim 1, wherein at least one keying feature is formed inthe overmold material between magnetic poles of the stator assembly. 12.The stator assembly of claim 11 wherein the keying feature includesslots formed in the overmold material between the magnetic poles withwidths of at least two of the slots being different.
 13. The statorassembly of claim 1, wherein the plurality of magnets includes fourmagnets, the stator assembly having a first magnetic pole defined by twoof the magnets that are adjacent to each other and a second magneticpole defined by the other two of the magnets that are adjacent to eachother, the overmold material molded to have a first slot between themagnets of the first and second magnetic poles on a first side of theflux ring and a second slot between the magnets of the first and secondmagnetic poles on a second side of the flux ring that is diametricallyopposed to the first side of the flux ring, the first and second slotshaving different widths.
 14. A stator assembly comprising: a housing; aflux ring disposed within the housing, the flux ring having a seam thatallows the flux ring to be compressed for insertion into the housingduring assembly; a plurality of permanent magnets disposed around aninner surface of the flux ring, each magnet disposed between at leasttwo anchors extending radially inwardly from an inner surface of theflux ring; and a material overmolded around the plurality of magnets tosecure the magnets to the flux ring, to secure the flux ring to thehousing by expanding the flux ring against the housing and to preventthe flux ring from compressing by filling the seam of the flux ring. 15.The stator assembly of claim 14 wherein one of the flux ring and thehousing includes at least one projection and the other of the flux ringand the housing includes at least one hole in which the at least oneprojection is received, the seam of the flux ring aligned with a firstmagnetic pole of the stator assembly.
 16. The stator assembly of claim15 wherein the projection and hole of the flux ring and housing disposedabout ninety degrees from the seam of the flux ring.
 17. The statorassembly of claim 15 wherein the projection and hole of the flux ringand housing are aligned with a second magnetic pole of the statorassembly.
 18. The stator assembly of claim 14, wherein at least onekeying feature is formed in the overmold material between magnetic polesof the stator assembly, the keying feature including slots formed in theovermold material between magnetic poles of the stator assembly when theovermold material is molded with widths of at least two of the slotsbeing different.
 19. A stator assembly comprising: a housing; a fluxring disposed within the housing; a plurality of permanent magnetsdisposed around an inner surface of the flux ring; a material overmoldedaround the plurality of magnets to secure the magnets to the flux ring;and at least one of a rear bearing support, front bearing support andfan baffle integrally formed of the overmold material during molding ofthe overmold material.
 20. A power tool comprising: a housing; and amotor disposed within the housing and having an output coupled to atransmission, the motor having a stator assembly having a flux ringdisposed within a stator housing, a plurality of permanent magnetsdisposed around an inner surface of the flux ring, and a materialovermolded around the plurality of magnets to secure the magnets to theflux ring and secure the flux ring to the stator housing.
 21. The powertool of claim 20, wherein the flux ring includes anchors extendingradially inward and each of the plurality of permanent magnets isdisposed between at least two of the anchors.
 22. The power tool ofclaim 20, wherein the flux ring includes a seam that allows the fluxring to be compressed for insertion into the housing during assembly ofthe stator assembly, the overmold material expanding the flux ringagainst the stator housing.
 23. The power tool of claim 22 wherein theseam of the flux ring is filled with the overmold material that preventsthe flux ring from compressing.
 24. The power tool of claim 22 whereinthe seam is aligned with a magnetic pole of the stator assembly.
 25. Thepower tool of claim 20, wherein one of the flux ring and the housingincludes at least one projection and the other of the flux ring and thehousing includes at least one hole in which the projection is receivedto align the flux ring in the housing.
 26. The power tool of claim 25,wherein the projection and hole of the flux ring and housing aredisposed about ninety degrees from the seam of the flux ring.
 27. Thepower tool of claim 25, wherein the stator assembly includes at leastone of a rear bearing holder, front bearing holder and fan baffleintegrally formed of the overmold material during molding of theovermold material.
 28. The power tool of claim 25, wherein the overmoldmaterial is a plastic.
 29. The power tool of claim 20, wherein at leastone keying feature is formed in the overmold material between magneticpoles of the stator assembly, the keying feature including slots formedin the overmold material between the magnetic poles when the overmoldmaterial is molded with widths of at least two of the slots beingdifferent.
 30. A method for constructing a permanent magnet statorassembly comprising: inserting a flux ring having a plurality of anchorsextending radially inward into a housing; inserting a plurality ofpermanent magnets between the anchors; injecting a material around thepermanent magnets in the flux ring so that the material at leastpartially overmolds the permanent magnets to secure the permanentmagnets to the flux ring and expand the flux ring against the housing tosecure the flux ring to the housing.
 31. The method of claim 30, whereinthe flux ring includes a seam that allows the flux ring to be compressedand inserting the flux ring into the housing includes compressing theflux ring before inserting into the housing, inserting the flux ringinto the housing while the flux ring is compressed and allowing the fluxring to expand against the housing once it has been inserted into thehousing.
 32. The method of claim 31, and further including preventingthe flux ring from compressing by injecting the material so that itfills the seam of the flux ring, the material hardening in the seam andpreventing the flux ring from compressing.
 33. The method of claim 30,further including aligning the flux ring in the housing by inserting theflux ring in the housing so that a projection in one of the housing andflux ring extends into a hole in the other of the flux ring and thehousing.
 34. The method of claim 30, further including injecting thematerial so that it forms at least one of a rear bearing holder, a frontbearing holder and a fan baffle.
 35. The method of claim 30, furtherincluding injecting the material to form at least one keying feature byforming slots in the material between magnetic poles of the statorassembly with widths of at least two of the slots being different. 36.The method of claim 30, and further including preassembling the housingand flux ring as a unit by: stamping the housing and flux ring fromseparate blanks, the separate blanks each stamped to have interlockingfingers on opposed ends; stamping at least one hole in one of thehousing and flux ring blanks and stamping at least one projection in theother of the housing and flux ring blanks; laying the housing and fluxring blanks together with the at least one hole and the at least oneprojection engaging each other; and rolling the housing and flux ringblanks so that the fingers of the housing blank interlock and thefingers of the flux ring blank interlock.
 37. The method of claim 36 andfurther including spot-welding the flux ring and housing together. 38.The method of claim 30, and further including preassembling the housingand flux ring as a unit by: rolling the flux ring from a blank; androlling the housing from a blank where the housing blank is rolledaround the flux ring with the flux ring acting as a rolling arbor. 39.The method of claim 38 wherein one of the flux ring and housing blanksis stamped to have at least of one projection and the other of the fluxring and housing blanks is stamped to have at least one hole therein,the at least one projection engaging the at least one hole during therolling of the housing blank about the flux ring.
 40. The method ofclaim 38 wherein the flux ring and further including spot-welding theflux ring and housing together.